Peripheral Opioid AnalgesiaMary Cranford Figliola, Master of Science, 1999 Thesis directed by Brian M. Cox, Ph.D, Chairman, Department of Ph anna co logy Exogenous and endogenous opioid compounds are known to have analgesic effects.Endogenous opioid compounds include endorphin, enkephalin and dynorphin which are differentially processed from precursor peptides depending on the site of their production.These peptides exert their effects through at least three opioid receptors: mll, delta and kappa. Exogenous opioid compounds can exert a more potent analgesic action but are accompanied by deleterious side effects including respiratory depression and addiction.These side effects are centrally mediated and until recently the analgesic actions of opioids were believed to occur in the CNS as well . Recent laboratory and clinical studies indicate that in the presence of inflammation endogenous and exogenous opioids have analgesic effects in the periphery. Certain immune factors are involved resulting in increased endogenous opioid peptides at the site of injury and resulting in increased opioid receptors at the nerve terminal allowing for peripheral opioid analgesia.